Purpose: To investigate, by means of spectral domain optical coherence tomography, retinal reflectivity changes as an early biomarker anticipating radiation-induced macular edema (ME) in patients treated by iodine-125 (I-125) brachytherapy.
Methods: Thirty patients planned for I-125 brachytherapy because of uveal melanoma were prospectively included and followed every 4 months for five years. Reflectivity alterations, namely hyperreflective retinal foci, were characterized and counted by two independent masked examiners by means of spectral domain optical coherence tomography imaging. Hyperreflective retinal foci were defined as discrete intraretinal reflectivity changes ≤30 µm, with reflectivity similar to nerve fiber layer and without back shadowing.
Results: Macular edema occurred in 17 patients (24.2 ±15.1 months) (group 1) after irradiation. Thirteen patients showed no signs of ME at the 5-year follow-up (group 2). The number of hyperreflective retinal foci was statistically higher in sequential visits until the evidence of ME in group 1 vs group 2 (P < 0.0001). In group 1, hyperreflective retinal foci at the follow-up before the evidence of ME were significantly related to the OCT central subfield thickness at ME appearance (P = 0.0002, r2=0.6129). The intergrader agreement was almost perfect (intraclass correlation coefficient = 0.80).
Conclusion: Hyperreflective retinal foci may be considered as an early in vivo imaging biomarker of retinal inflammatory response to ocular irradiation, anticipating the development of radiation maculopathy.